Methods for the manufacture of a contact strip folded in zigzag for a fixed switching contact and folding machines for performing said methods

ABSTRACT

A method and a machine for the manufacture of a zigzag folded metal contact strip for a fixed contact which permanently snugly encloses an axially movable switching rod of an electric switch, said strip being alternately bent in said machine in one and in the other direction out of its plane over the foremost teeth of two cooperating sets of intermittently movable teeth.

O United States Patent 51 3,641,803

Schuurbiers et a1. 1 1 Feb. 15, 1972 [54] METHODS FOR THE MANUFACTURE 56 ierences cru OF A CONTACT STRIP FOLDED 1N ZIGZAG FOR A FIXED SWITCHING UNTED STATES PATENTS CONTACT AND FOLDING MACHINES 2,397,582 4/1946 Watt et a1. ..72/405 FOR PERFORMING SAID METHODS 2,047,717 7/1936 Van Dresser et al. .140/105 2,329,789 9/1943 Schank et a1. ..72/187 72 lnvemors; p n- Schuurbiers, Harmelcn; Louis 3,199,175 8/1965 Wogerbauer ..140/105 Verhagen; Johannes G. L. Vernhout, both of Utrecht, all of Netherlands Primary Larson Att0rneylmirie, Smiley, Snyder & Butrum [73] Assignee: N.V. COQ, Kanaalweg, Utrecht, Netherlands [5 7] ABSTRACT Filedi L 20, 1969 A method and a machine for the manufacture of a zigzag folded metal contact strip for a fixed contact which per- [21] Appl' 867;, manently snugly encloses an axially movable switching rod of an electric switch, said strip being alternately bent in said [30] Foreign Application Priority Data machine in one and in the other direction out of its plane over the foremost teeth of two cooperating sets of intermittently Apr. 24, 1969 Netherlands ..6906378 movable math:

[52] US. Cl ..72/381, 72/187, 72/190, 72/385 [51] Int. Cl ..B21d 13/00 [58] Field of Search ..72/190, 384,385,405; 11 Claims, 7 Drawing Figures I NVE NTOR S PATENTEUFEB 1 5 I972 SHEET 1 OF 3 s T R N u x m E 0 /M m B G H ..I-// N f P t 1: 0 G? M Wm R M 1/ min 3 u 5 r wmwmflwwuflfi fir "r? "b t "W2 5 v L L G J A I H U h Rm 9 7 U u N 0 A v I I 1 l P L H 8 I n ATTORNEYS PATENTEBFEBISIQYZ 3.641.803]

INVENTORS PETRl/S I SCHUURBiERS Laws A VERHAGEN J'OHANNES G L. VERNHOUT PATENTEBFEB i 5 m2 SHEET 3 UP 3 INVENTORS J. SCHUURBiERS A- VERHAGEN 6 L. VERNHOUT PTUS Lav/S EQHANNES @V W ATTORNEYS METHODS FOR THE MANUFACTURE OF A CONTACT STRIP FOLDED IN ZIGZAG FOR A FIXED SWITCHING CONTACT AND FOLDING MACHINES FOR PERFORMING SAID METHODS The invention relates to a method and a bending machine for the manufacture of a zigzag folded metal contact strip for a fixed contact which permanently snugly encloses an axially movable switching rod of an electric switch of large power and electrically conductively connects said switching rod with the end of the electric circuit to be closed and opened by said switch.

Up to now a flat metal strip was passed with ample clearance between intermeshing toothed wheels in order to give it the required zigzag shape. However, it has appeared that in the thus formed zigzag contact strip material stresses of undefined magnitude occur in places which can not be determined in advance. Said stresses make it impossible to make the contact pressures of all parts of the contact strip lying against the switching rod equal.

The invention has the object to provide a method and a machine for folding a metal strip in zigzag, in which said material stresses occur in predeterminable places of the strip and are equal in all corresponding places, so that the contact strip will clasp the switching rod tightly with an evenly distributed force. This is attained in that in the bending machine the strip of metal, from which the contact strip is formed, is alternately bent in one and in the other direction out of its flat surface over a movable tooth which, during the bending operation, is kept in place. In this manner of deformation the deformation occurs only in the folds of the zigzag-shaped strip. Since furthermore the parts of the zigzag-shaped strip enclose, at the folds, the same angles, the material stresses due to its folding are equal, so that the parts of the contact strip come to lie against the switching rod with the same contact pressure.

The bending machine for carrying out the described method can advantageously be provided with a holder, two sets of at least two equal movable teeth positioned side by side, said sets of teeth facing each other in said holder, the active end portion of each tooth having two inclined flanks adjoining each other in an end edge, the teeth of one set extending with their active end portions between and next to the active end portions of the teeth of the other set with sufiicient clearance for the strip which has to be passed between said sets, means for the periodic removal of the two teeth, which are found on the strip discharge side of the sets of teeth, from said sets, means for shifting the sets of teeth together from the strip-receiving side to the strip discharge side of said sets for a distance which is equal to the thickness of one tooth, means for returning the teeth removed from said sets one after the other to the stripreceiving side of the sets of teeth and a device found in the holder in front of the strip-receiving side of the sets of teeth and adapted to be moved transversely to the shifting direction of said sets for guiding the still unbent part of the strip to be passed through the sets of teeth and for bending said strip part over the tooth which is returned latest to and kept in its place on the strip-receiving side of the sets of teeth.

For the manufacture of a contact strip, of which the folds, which come to lie against the switching rod, are forced a bit aside to obtain substantially tubular contact places, the bending machine may be constructed in such a manner, that the teeth of one set are each provided near the root of their flanks facing the strip discharge side of the sets of teeth with a transverse groove formed in said flanks and a movable pressing tool is provided behind the strip discharge side of said set, by means of which the bent part of the strip lying against said flank of the tooth found on the strip discharge side of said sets can be forced with its fold into said groove. The thus formed substantially tubular contact places are preferably a bit curved in the axial direction of the tube to facilitate the movement of the switching rod through the fixed contact provided with the zigzagshaped contact strip. To obtain this curvature the transverse groove and the adjacent area of said tooth flank may have each in their transverse direction a concave shape and the pressing surface of the pressing tool may have a corresponding convex shape in its transverse direction.

As it is preferred to make the active end portions of the teeth and, consequently, the folds formed by bending the strip not too acute, but on the other hand to make the folds so acute that the largest possible number of contact places between the contact strip and the switching rod is obtained, the bending machine may be provided behind the strip discharge side of the sets of teeth with a movable pushing member, by means of which at least the parts of the strip which adjoin each other in the folds found on one side of the zigzag folded strip discharged form the sets of teeth can be forced towards one another. The invention will be further elucidated with the aid of the drawing; therein is:

FIG. 1 partly an axial sectional view, partly an elevational view of a portion of a switching rod and a fixed contact, which is in permanent contact with said rod, of a switch of large power constructed in accordance with the invention,

FIG. 2 a cross-sectional view taken on the line IIII in FIG.

FIG. 3 a perspective view of a portion of a contact strip for the meant fixed contact of such a switch,

FIG. 4 partly a vertical sectional view, partly anelevational in view of a machine for the manufacture of a zigzag-shaped contact strip,

FIG. 5 a horizontal cross-sectional view taken on the broken line V-V in FIG. 4,

FIG. 6 a vertical cross-sectional view taken on the line VI- VI in FIG. 4 and FIG. 7 on a larger scale and in perspective some details of the machine shown in FIGS. 4, 5, 6.

In FIGS. 1 and 2 an axially movable switching rod of an electric switch of large power is designated by 1. For the permanent connection of the switching rod 1 with the external circuit a fixed contact is provided which consists of an annular metal holder 2 and a contact strip 3 supported by said holder. The contact strip 3 consists of a zigzag folded metal strip which is bent in the shape of a ring clasping tightly around the switching rod 1. The parts 3', 3 of the folded strip 3 extend in pairs closely together and substantially parallel to each other and they are directed almost tangentially to the switching rod 1. It appears from FIGS. 2 and 3, that the contact strip 3 lies against the switching rod with portions in the shape of a curved split tube 4 which is forced aside. The curvature of the tubular portion 4 is not necessary but it facilitates the movement of the switching rod 1 through the annularly bent contact strip 3.

The machine shown in FIGS. 4-7 for the manufacture of the zigzag folded contact strip 3 is provided with a holder 5 formed as a housing which consists in a manner not indicated of detachably interconnected parts, so that all members and parts can be mounted therein. The machine is provided with a set of movable vertical teeth 6 which are positioned side by side and a set of movable vertical teeth 6" positioned one next to the other. Each tooth 6', 6" is provided with an active end portion 7, 7" having inclined flanks 9, 9" adjoining each other in an end edge 8', 8" and with two horizontally projecting portions l0, 10" by means of which the tooth is adapted to engage guiding grooves 11', 12', 11", 12 of the holder 5. The end portions 7 of the teeth 6' extend between and next to the end portions 7" of the teeth 6" with sufficient clearance to receive the metal contact strip 13 to be passed through the sets of teeth 6', 6", when the teeth 6', 6" engage with their projecting portions 10, 10 the guiding grooves 11', 11''. The teeth 6', 6" can be moved from the left (the strip-receiving side) to the right (the strip discharge side) by means of horizontally movable forks 14, 14'' for a distance which is equal to the thickness of one tooth. The teeth 6', 6 lying on the strip discharge side are found in vertically movable slides 15', 15'', by means of which these teeth can be vertically removed from the interrneshing sets of teeth 6, 6" and can be positioned with their projecting portions 10', 10" in front of guiding grooves 12, 12". The teeth 6', 6" can be pushed out of the slides 15', 15" and through the guiding grooves 12', 12" into similar vertically movable slides 17', 17" by means of horizontally movable pushing members 16, 16''. The slides l7, 17 are adapted to return the teeth 6, 6 to the stripreceiving side of the intermeshing sets of teeth 6', 6" into said sets.

In front of the sets of teeth 6', 6" a vertically up and down movable block 18 provided with guiding rollers 19 is mounted in the holder 5. The strip 13 to be folded in zigzag is passed through said rollers.

The described part of the machine operates as follows:

The machine starts in a condition, in which the forks l4, 14 are found in the lefthand end position and the left most teeth 6 and 6" are kept in the shown inactive position in the slides 17', 17" outside the intermeshing sets of teeth 6, 6", whereas the block 18 is in its uppermost position. The free end of the metal strip 13, which has to be bent, is then placed on the flank 9' of the leftmost tooth 6 of the active set of teeth 6. Thereafter the slide 17" carrying the tooth 6" is moved upwards, so that the strip 13 is kept in place between the teeth 6' and 6" in question. Thereupon the block 18 is moved downwards, so that the strip is bent over the end edge 8" of the tooth 6". Thereafter the slide 17' containing the tooth 6 is moved downwards and thereupon the block 18 is returned to its uppermost position, so that the strip 13 is bent over the end edge 8' of the tooth 6'. The strip 13 then has two parts of the required zigzag shape. After these manipulations have been finished, the slides 15', 15" containing teeth 6', 6" are vertically removed from the sets of teeth 6', 6". Thereafter the pushing members 16, 16" are first moved a bit to the left and immediately thereafter again to the right, in such a manner, that the teeth 6', 6" are pushed out of the slides 15', 15" and come to hang temporarily in the guiding grooves 12, I2". Thereafter the empty slides 15', 15" are returned to the shown starting position, whereafter the forks 14, 14 are moved to the right, so that the sets of teeth 6', 6" are pushed to the right for a distance, which is equal to the thickness of one tooth, and the slides l, 15" receive again a tooth 6, 6". The slides 17 17" then are vertically removed from the sets of teeth 6, 6", whereafter the teeth hanging in the guiding grooves 12', 12" are forced by the pushing members 16', 16" into the slides 17, 17". Thereupon the forks 14', 14" are returned to their left-hand end position. The machine is then restored to its starting condition, whereafter first the slide 17" carrying the tooth 6 is moved upwards again, then the block 18 and the rollers 19 are moved downwards, etc.

To form the tubular portions 4 on the contact strip 13 the teeth 6' are each provided with a transverse groove 20 in their flank 9' facing the discharge side of the sets of teeth 6', 6". Furthermore a vertically movable block 21 comprising a pressing tool 22 constructed as a pivotable pawl is provided. This pressing tool is forced upwards by means of a fixed stop pin 23, when the block 21 is moved downwards, so that the pressing surface 24 of said tool is forced towards to transverse groove 20 of the tooth 6 contained in the slide 15. In that condition at least the fork 14' is moved to the right as far as possible, as is shown in FIG. 4, so that the upper fold of the zigzag folded strip 13 lying against the free flank 9' of said tooth 6' is forced by the pressing pawl 22 into the groove 20. From FIG. 7 it appears, that the groove 20 is curved in the transverse direction of the teeth, so that, since the pressing surface 24 of the pressing pawl 22 has a corresponding trans verse curvature, the tubular upper fold 4 of the strip 13 obtains the curved shape shown in FIG. 3.

Finally the machine is provided with a horizontally movable block 25 having a pawl-shaped pushing member 26. This pushing pawl 26 is pressed against the tubular fold 4' (FIG. 4) of the strip 13, which has just come out of reach of the sets of teeth 6', 6" and the pressing pawl 22, 24. The tubular folds 4 of the strip 13 are forced by the pushing pawl 26 towards each other as closely as possible. The completed zigzag bent strip 13 is discharged from the machine through a tube 27. Pieces of predetermined length are then cut off from this strip and thereafter the contact strips are manufactured by bending said pieces.

The forks 14, 14', the slides 15', 15'', the pushing members 16', 16', the slides 17, 17", the block 18, the block 21 and the block 25 are respectively coupled by rods 28', 28", 29', 29", 30', 30", 31', 31", 32, 33 34 with mechanical, hydraulical or pneumatical driving means, which are not shown.

We claim:

I. A bending machine for the manufacture of zigzag folded metal contact strips adapted to be used in electrical switches which may be called upon to conduct heavy current loads, said machine comprising, in combination:

a holder assembly having a strip-bending region and a folded strip delivery region disposed in spaced relation to each other and defining a strip-translating space therebetween;

a first set of separate bending teeth associated with one side of said strip-translating space and a second set of separate bending teeth associated with the other side of said striptranslating space, each tooth having a tip defining a bending edge;

guide means for guiding said first and said second sets of teeth in tip-meshed condition from said bending region to said delivery region along said strip-translating space and including first means defining a recirculation path for said first set of teeth from said delivery region back to said bending region, and second means defining a recirculation path for said second set of teeth from said delivery region back to said bending region;

tooth-moving means for withdrawing one tooth of each set from tip-meshing condition at said delivery region to commence recirculation thereof and for translating the remaining tip-meshed teeth of the two sets toward said delivery region;

carrier means spaced from said bending region for moving a strip of indefinite length delivered to the tip-meshed teeth back and forth from said one side of said work-translating space to said other side thereof; and

means for sequentially completing recirculation of teeth of said first and second sets to said bending region whereby movement of said carrier means effects bending of the strip sequentially over the edges of said teeth.

2. The bending machine as defined in claim 1 wherein the tip of each tooth of said first set on that side thereof facing said delivery region is provided with a transverse groove, and pressing means for forcing strip folds formed by the tips of the teeth of said second set into each transverse groove at said delivery region.

3. The bending machine as defined in claim 8 wherein the tip of each tooth of said first set is concave in the transverse groove-defining surface thereof and said pressing means is correspondingly convex.

4. The bending machine according to claim 3 including pusher means for closing those folds formed by the tips of the teeth of said second set.

5. The bending machine according to claim 1 including pusher means for closing those folds formed by the tips of the teeth of said second set.

6. The bending machine as defined in claim 1 wherein the tip of each tooth is of wedge-shaped configuration defining the bending edge thereof at the apex of the tip.

7. The bending machine as defined in claim 1 wherein said tooth-moving means comprises first and second withdrawing members associated with the first and second sets of teeth respectively, and first and second yoke members associated with said first and second sets of teeth.

8. The bending machine as defined in claim 7 wherein said tooth-moving means also includes first and second pushing members associated with said first and second sets of teeth.

9. The method of forming zigzag folded metal contact strips for use in electrical switches which may be called upon to conduct heavy current loads, which comprises the steps of:

. positioning the end of a metal strip of indefinite length at e. bending the strip over the edge of said recirculated tooth a bending region and clamping it thereat between opby moving the strip in the opposite direction to that of posed flanks of one pair of bending teeth of two sets step thereof; f. repeating steps (d) and (e) to form a zigzag folded metal bending the strip over an edge of one tooth of said pair by 5 Strip Ofindefiniie gt i moving the strip transversely normal with respect to the The method according to clalm 9 Including the p of plane fth i deforming alternate folds into generally curved, cylindrical translating the pair of teeth toward a discharge region configuration through a distance equal to the width f one tooth; 11. The method according to claim 10 lncludlng the step of clamping the strip between said one tooth and a recircu- 10 closmg the remammg folds upon each otherlated tooth of the other set of teeth; 

1. A bending machine for the manufacture of zigzag folded metal contact strips adapted to be used in electrical switches which may be called upon to conduct heavy current loads, said machine comprising, in combination: a holder assembly having a strip-bending region and a folded strip delivery region disposed in spaced relation to each other and defining a strip-translating space therebetween; a first set of separate bending teeth associated with one side of said strip-translating space and a second set of separate bending teeth associated with the other side of said striptranslating space, each tooth having a tip defining a bending edge; guide means for guiding said first and said second sets of teeth in tip-meshed condition from said bending region to said delivery region along said strip-translating space and including first means defining a recirculation path for said first set of teeth from said delivery region back to said bending region, and second means defining a recirculation path for said second set of teeth from said delivery region back to said bending region; tooth-moving means for withdrawing one tooth of each set from tip-meshing condition at said delivery region to commence recirculation thereof and for translating the remaining tipmeshed teeth of the two sets toward said delivery region; carrier means spaced from said bending region for moving a strip of indefinite length delivered to the tip-meshed teeth back and forth from said one side of said work-translating space to said other side thereof; and means for sequentially completing recirculation of teeth of said first and second sets to said bending region whereby movement of said carrier means effects bending of the strip sequentially over the edges of said teeth.
 2. The bending machine as defined in claim 1 wherein the tip of each tooth of said first set on that side thereof facing said delivery region is provided with a transverse groove, and pressing means for forcing strip folds formed by the tips of the teeth of said second set into each transverse groove at said delivery region.
 3. The bending machine as defined in claim 8 wherein the tip of each tooth of said first set is concave in the transverse groove-defining surface thereof and said pressing means is correspondingly convex.
 4. The bending machine according to claim 3 including pusher means for closing those folds formed by the tips of the teeth of said second set.
 5. The bending machine according to claim 1 including pusher means for closing those folds formed by the tips of the teeth of said second set.
 6. The bending machine as defined in claim 1 wherein the tip of each tooth is of wedge-shaped configuration defining the bending edge thereof at the apex of the tip.
 7. The bending machine as defined in claim 1 wherein said tooth-moving means comprises first and second withdrawing members associated with the first and second sets of teeth respectively, and first and second yoke members associated with said first and second sets of teeth.
 8. The bending machine as defined in claim 7 wherein said tooth-moving means also includes first and second pushing members associated with said first and second sets of teeth.
 9. The method of forming zigzag folded metal contact strips for use in electrical switches which may be called upon to conduct heavy current loads, which comprises the steps of: a. positioning the end of a metal strip of indefinite length at a bending region and clamping it thereat between opposed flanks of one pair of bending teeth of two sets thereof; b. bending the strip over an edge of one tooth of said pair by moving the strip transversely normal with respect to the plane of the strip; c. translating the pair of teeth toward a discharge region through a distance equal to the width of one tooth; d. clamping the strip between said one tooth and a recirculated tooth of the other set of teeth; e. bending the strip over the edge of said recirculated tooth by moving the strip in the opposite direction to that of step (b); and f. repeating steps (d) and (e) to form a zigzag folded metal strip of indefinite length.
 10. The method according to claim 9 including the step of deforming alternate folds into generally curved, cylindrical configuration.
 11. The method according to claim 10 including the step of closing the remaining folds upon each other. 